A characteristic of digital audio and video signals is the sampling rate, which is the number of samples per unit time (e.g., second) taken from a continuous signal to form a discrete signal. The concept of re-sampling digital signals, such as audio and video signals, to obtain a new sampling rate is well known. If the new sampling rate is higher than the original sampling rate, the re-sampling process is commonly referred to as upsampling. Conversely, if the new sampling rate is lower than the original sampling rate, the re-sampling process is commonly referred to as downsampling.
In some signal processing applications, it is desirable to synchronize multiple digital signals. To synchronize a given digital signal with respect to a reference signal, it is resampled such that the new sampling rate is equal to that of the reference signal, or some ratio thereof. At the same time, the timing of the resampled signal is matched to the reference signal.
For example, television broadcast signals typically have audio and video components, where the audio sampling rate is lower than the video sampling rate (e.g., 48 kHz audio and 27 MHz video). When generating the broadcast signal, if the source audio signal is not sampled at 48 kHz, or if the audio signal is not synchronized with the video signal clock, the audio signal is resampled to the desired 48 kHz sampling rate and locked to the video signal clock according to a 48/27000 ratio.
In another example, a digital audio router may switch tens or even hundreds of audio channels. To enable efficient switching, it is desirable for each audio channel signal to be synchronized to a reference sample rate by resampling.